Guterres got off to a smooth start – professional and low-key, almost invisible in the media. The beginning of Trump's term has been dogged by scandal, making front pages every day in every newspaper.

That's not the only difference. The new American president's isolationism and protectionism goes against everything that the U.N. is about: openness, free trade, international cooperation. Some of Trump's statements – that torture works, that refugees should be denied entry, that Muslims should be subject to extreme vetting – contradict principles globally accepted by the United Nations 70 years ago.

Trump has called the U.N. an organization where people "just talk and have a good time", like a businessman who eschews one big corporation and switches his deals to its competition.

This isn't how international relations works, and Trump's oft-changing, emotion-driven statements have not only raised eyebrows – they are also deteriorating U.S. relations with various countries, including China, Muslim and Arab nations, Mexico and Australia.

Concerns about the close relationship between the Trump administration and Vladimir Putin's Russia, and Trump's changing views on the need for NATO have produced waves of anger and fear in Ukraine, the Baltic States and elsewhere in Eastern Europe.

After only a few weeks the "America first" policy has put America last in terms of global respect.

Trump in the White House might be the biggest challenge the U.N. has ever faced, and it puts Guterres in a very delicate position. A cozy relationship with Trump will make Guterres seem a spineless Secretary General, mocked by many member-states. But confrontation with the United States will impoverish and isolate the U.N., upsetting both the international civil service and U.N. member-states.

These prior posts give him confidence in his leadership and ensure that he not only knows the world very well but is also fully aware of what it takes to efficiently manage a large international organization.

Trump and Guterres would like to see a more efficient, better managed and less costly United Nations. So if Guterres can create an image of himself as a reformist, open to do business differently and non-ideologically, he may find a way to work with Trump.

Cutting unnecessary expenditures, reducing the number of special representatives and working quietly on issues such as anti-corruption, action on sexual abuse by peacekeepers, the protection of whistle-blowers and independent oversight will earn sympathy from Washington.

Guterres is also operating from a position of relative strength vis-a-vis the U.S. president. His victory as U.N. chief was solid and steady, without serious competition from any other candidates. As a result, he managed to avoid making deals with member states to support him in exchange for economic aid and or high posts.

It is important to note that Guterres has won applause for immediately appointing three women to top posts (appeasing many who protested the fact that the U.N. would again be led by a man).

Such widespread support will allow Guterres to remain relatively free from internal pressures. This means he does not really need to kowtow to Donald Trump.

By the time Guterres begins thinking about a second term in five years – effectively his only reason to be beholden to the five permanent members of the U.N. Security Council, which includes the United States – there may well be a different American leader.

And bowing to Trump may lead Gutteres to lose face in front of some of those whom he will need votes from to be re-elected.

Bon ton and understanding

Instead, Guterres can capitalize on his wisdom, knowledge and experience, filling the gaps in global governance that Trump creates with his antagonistic and ill-advised foreign policy. In contrast to Trump, who might shout and offend, Guterres can offer what the French call bon ton, understanding and reasonableness in the coming years.

Already, Guterres has set up a plan of action for his mandate. He will support the efforts of the Security Council's permanent member on counterterrorism and the Islamic State, on sanctions, non-proliferation and North Korea while he, as secretary-general, will lead efforts to prevent conflicts, mitigate climate change, eliminate poverty and pursue other items from the 2030 Agenda.

This is a good division of labor, in which the U.N. focuses on prevention and the kind of "soft" security issues it is well suited to, while Trump, Putin, Theresa May and the next French president deal with "hard" security issues such as Syria, Iran and North Korea.

It may also help the world better understand what the U.N. can and cannot do and stop blaming it inappropriately, for the Syrian catastrophe, for example, and also make clear what the major powers can and should do.

The climate change and human rights challenges

Two major tests for Guterres during the Trump presidency will be climate change and human rights.

If Trump follows through on these threats, he will almost certainly provoke a backlash from China and other developing countries, including India, which ratified the Paris climate agreement with the understanding that they would receive financing and technology from rich nations.

Guterres has to mobilize U.N. member-states to fill the gap left by Trump. Paradoxically, the Chinese, so unfairly accused by Trump of "inventing" climate change, are the ones who can show a global example on how to mitigate the CO2 emissions and invest in renewable energy. They may prove a strong partner in U.N.'s efforts to save the environment.

Similarly, the proposed (but thus far constitutionally blocked) ban on citizens of seven Muslim-majority countries entering the United States is not just an American problem. It recalls the dark ages of religious discrimination, stokes enormous global tensions and creates grounds for xenophobia, terrorism and more conflicts.

Women's and girls' rights are also now in jeopardy around the world. Trump and his vice president have taken a strong anti-abortion stance and even reissued a global gag rule prohibiting international health providers that receive U.S. funding from even talking to patients about abortion.

China will not come to the rescue on human rights. Guterres will probably have to rely on European and Latin American member states to keep the U.N. machinery working and find a way to act as the global guardian of the international norms and principles that have sought to safeguard human rights around the world since 1948.

On both climate change and human rights, strong leadership by Guterres could irk Trump, who would see him posing as a moral global leader. Guterres will also need to work with the United States to secure funding and support. Still, it is likely he will have to confront Trump at times when the president's statements or policies undermine international law and order.

He should also try to properly frame critical issues in ways that resonate with reasonable people in Trump administration. On climate change, for instance, Guterres can attempt to formulate opportunities that renewable energy would present for job creation and innovation, including in the United States.

Guterres may search for a cooperative approach to peacekeeping and conflict prevention, presenting them as burden-sharing exercises in line with, rather than in opposition to, U.S. national interests. Because U.N. peacekeeping is eight times less expensive than the comparable U.S. forces needed to do the same job, there's a good economic argument to be made to the businessman sitting in the Oval Office for his continued U.N. investment.

Even if the United States delays paying its budgetary contributions to the U.N., Guterres can use this as a leverage to push for reducing bureaucracy and structural reforms.

It is in Guterres' interests to learn to adapt to Trump. Boutros-Ghali could not work with Washington even when the administration was multilateralism-friendly. He lost his second term, but more importantly, the weakened U.N. was unable to respond to the massacres in Rwanda and Srebrenica. Those failures continue to haunt the institution today.